GRACE Documentation

University of Colorado Real-Time GRACE Data Analysis Site

GRACE Related Sites

Center for Space Research (CSR)

GeoForschungs-
Zentrum Potsdam (GFZ)

GRACE Tellus

JPL PO.DAAC

How to Use this Site

Overview

This website provides an online interface to a series of data analysis routines written in the Interactive Data Language (IDL) by Sean Swenson. Computations are performed in real-time, using parameters specified by the user. End products are either maps or time series, and may be downloaded as ascii files. Images are passed to the browser as jpeg files of modest size, and can also be saved. Data obtained from this site should be referenced with wording such as "... data obtained from the University of Colorado GRACE Data Analysis Website - http://geoid.colorado.edu/grace/grace.php".

Map View

Update Map

A new map, using the most recently selected parameters, is generated by clicking the Update Map button at bottom.

Plot Type

Maps can be produced for the following quantities: Annual Amplitude, Annual Phase, RMS (Temporal), RMS about the Annual Cycle, Trend, Monthly Anomaly (with respect to static field), and Temporal Mean (i.e. the static field).

Latitude / Longitude

A sub-region of the map can be selected manually by entering numerical values for the extreme values of a window. Expected values are [-90:90] for latitude and [-180:180] for longitude. The "Reset" button will return the values to their original values.

Scale

The scale of the plot can be specified by entering numerical values. The "Reset" button will return the values to their original values.

Smoothing Radius

The radius (half-width, half-maximum) of the Gaussian filter used to smooth the GRACE data can be specified by entering numerical values.

Action

The "Action" pulldown menu can be used to change the mode from "Zoom" to either "Time Series" or "Time Series Basin" (see below). After choosing one of these menu items, clicking on the map will generate a new map or time series plot.

Zoom Factor

When "Zoom" is selected, clicking on the map produces a map centered at the chosen point, in a window reduced in size by the value of "Zoom Factor". "Zoom Factor" can be increased for rapid zooming, or one can zooms successively.

Map Annotations

Maps can be overlain with various geographic information. The "Local Projection" button changes the map projection and is most useful at high latitudes.

Time Series

After choosing one of the Time Series items from the "Action" pulldown menu, clicking on the current map will produce a time series plot for either the selected point, or for the spatial average of the river basin containing that point. Each land point is associated with a single river basin; no sub-basins can be selected.

Time Series Seasonal Fit

Choosing one of the menu items under "Time Series Seasonal Fit" will overlay the current time series with a best-fitting seasonal comprised of: an annual plus a temporal mean; an annual, a mean, and a trend; an annual, a semi-annual, and a mean; or an annual, a semi-annual, a mean, and a trend.

Error Bars

Uncertainty due to errors in the GRACE data based on the method described in Wahr et al. [2004] GRL paper can be overlain on the current time series.

Data Center / Release

Currently available datasets are CSR RL04, GFZ RL04, and JPL RL04. As described in

Downloading Data

Data can be downloaded by selecting the "Make data export available for download" button. For subsequent actions, a button will appear below the map saying "download text data". Push this button to download an ascii file. The data made available will be that corresponding to the most recent action taken, i.e. either map data or time series data. Images can be saved directly from the browser.

Disclaimer:

Data is provided with the understanding that it is not guaranteed to be correct or complete and conclusions drawn from such information are the sole responsibility of the user.

This work is supported by the NASA Research, Education, and Applications Solution Network (REASON)